World’s biggest mobile phones maker, Nokia Oyj, is teaming up with Microsoft Corp. to challenge Google and Apple in the fast-growing smartphone market and set financial targets for the group.

Nokia shares fell 14%, the biggest drop in seven months, after its plan to make Microsoft’s Windows its primary software. This was seen as a sign of the extent of its troubles in taking on Apple’s iOS and Google’s Android platforms.

The move may be the biggest strategy shift by Nokia since the one-time wood pulp company began making mobile phones in the 1980s. According to sources, Stephen Elop, the new chief executive officer of the company, is struggling to revive Nokia after its piece of the fast-growing smartphone market plunged to 27.1% in the last quarter from 50.8% when Apple shipped its iPhone in June 2007. Nokia has lost more than 60% of its market value in that time.